Ammunition feed mechanism for machine guns



Sept. 5, 1950 E. c. M. D'Assls-FoNsEcA V2,521,345

AMMUNITION FEED MECHANI'SM FOR MACHINE GUNS Filed oct. 28, 1944 sheets-sheet 1 flag/.1:

Sept. 5, 1950 E. c. M. D'Assls-FoNsEcA 2,521,346

AMMUNITION FEED MECHANISM FOR MACHINE GUNS Filed Oct. 28, 1944 3 Sheets-Sheet 2 5, 1950 E. c. M. DAssls-FONSECA 2,521,346

AMMUNITION FEED MECHANISM FOR MACHINE GUNS Filed Oct. 28, 1944 3 Sheets-Sheet 5 Patented Sept. 5, 1950 AMMUN'ITION FEED MECHANISM FOR MACHINE GUNS Evelyn Cecil Muschamp dAssis-Fonseca, Bristol, England, assignor to The Bristol Aeroplane Company Limited, Bristol, England, a British Company Application October .28, 1944, -Serial No. 560,826 In Great Britain October 21, 1943 Section 1, Public Law 690, August, 1946 Patent expires October 21, 1963 1 Claim. 1

This invention concerns improvements in yor relating to ammunition feed-mechanisms for machine guns of the belt-fed type.

With machine guns of this type when the belt paths are long it has been found that the load on the feed mechanism of the gun is excessive. This is particularly the case when the lmachine guns are of large calibre (for instance in the socalled cannon provided in aircraft) where the weight of the ammunition and its belt is Very considerable.

The present invention has for its object to provide an ammunition feed-mechanism auxillary to that provided by the gun itself thereby considerably reducing the load on the latter.

According to the present invention an auxiliary, independent power-driven ammunition feed-mechanism for machine-guns `of the belt fed type is interposed between the source of supply and the gun, and is characterised in that the belt of ammunition is arranged to pass from the said feed-mechanism to the gun, by a variable .circuitous path and that variations .of the said path control the operation of the said feed mechanism. Preferably the construction is such that shortening of the said circuitous path is adapted to bring into operation the said feed mechanism.

2 Y Figure l3 is a view in the direction of arrow -III of .Fig-ure 2, v

According to another feature of the invent-ion an ammunition feed-mechanism for machine guns of the belt-fed type is characterised in that the ammunition belt is adapted to. extend from the feed-mechanism to the gun by a circuitous path, the rate at which the mechanism feeds the ammunition belt to the gun being dependent upon the amount .by which the length of lsaid path is reduced.

Preferably the mechanism is adapted to be brought into operation (upon the gunbeing operated whereby the length of ammunition belt-between the feed mechanism and the gun is reduced) to feed the ammunition .belt to the gun at either of two rates one of which is .adapted to correspond to one amount of reduction in the length of ammunition belt between the mechanism and the gun and the other to another amount 0f reduction in the length therebetween.

A specific embodiment of the present invention will now be described merely by way of example as applied to a turret-mounted gun for an aeroplane. The description will be made with reference to the accompanying drawings of which:

Figure 1 is an elevation of the turret showing the relative disposition of the cannon, ammunition feed mechanism' and ammunition supply,

Figure 2 is a View of the feed-mechanism with parts broken away and to an enlarged scale,

Figure 4 is a view partly in section showingcertain details of the driving mechanism which is incorporated in the ammunition feed-mechanism.

As generally shown in Figure l a pair of .cannon machine guns Ill are disposed within the turret so as to protrude through the cupola ll thereof. The latter is capable of being rotated upon aring l2 to effect thetraversing movement of the gun. The turret is provided with a platform I3 which carries the gunners seat `I 4 and the boxes of 1ammunition l5, the arrangement being that the platform rotates with the guns andthe cupola and carries the ammunition boxes and the gunner around with it.

The ammunition yboxes Yleach receive the arnmunition belt in a known manner .and the said belts pass from .the boxes .each upwardly Vto Aone of the guns. Y

The auxiliary feed-mechanism,- which is indicated in-general by the reference IS, is `disposed .between one of the ammunition .boxes I5 andthe associated gun .l0 so that for each kgun there ,is provided one such auxiliary feed mechanism. As will be .clear from Figure .1 the mechanism .t6 vis so disposed that only a relatively Vshort length of unsupported .ammunition belt lies between -the gun` le andthe mechanism, the greater lengthof belt extending between the ammunition box l5 and the feed-mechanism. The rlatter is therefore subjected to the greater part of the load due to the weight of the ammunition belt, the gun having to .carry only the .load .due to the shorter length.

The feed mechanism ycomprises a drum Il, (Figures 2 to 4) over vwhich the ammunition belt from the box l5 passes, an electric motor I8 (see Figure 4) for driving said drum so that the latter draws the belt .of ammunition from the box .and feeds it towards .the gun, anda floating arm I9 carrying an idler roller 2.2 which engages with the ammunition belt as it leaves the feeder-drum l1. The arm .i9 actuates a .pair of switches as will be hereinafter described, said switches being capable of putting the motor la into, and out of, operation. The arm .i9 is urged by a spring 420 (see Figure 2) to assume a position in whichthe motor yswitches referred to are open. In thisposition of the arm I3, the ammunition belt on leaving the drum .Il is made to assume a path of J- outline as shown at ila, 2lb in Figure 1. The curved part 2lb of this path is derived from the idler roller 2.2 which is carried at the free end 0f the .arm I S, 4and the straight part 2Ia is the path from the roller 22 up towards the gun. The path of J-outline constitutes a circuitous path which when shortened effects an upward movement of the roller 22 and arm I9.

The drum Il and its driving motor I8 form an integral unit as shown in Figure 4. The unit is removably mounted within a casing 23 so that in the event of breakdown it is readily replaceable. The drum casing 23 is formed with a downwardly directed mouth 2li into which the ammunition belt passes as it travels along the channel 25 from the box I5.

The feeder-drum Il is provided with a pair of sprockets 2l' spaced from each other along the length of the drum. The teeth of the sprockets 21 are capable of engaging the shells which, comprise or are carried in the ammunition belt, as the latter passes around the drum I'I on its way .to the gun.

Disposed within the drum Il is an epicyclic reduction gear 28 whereof the driven element 29 V,is secured to the drum I1 whilst the driving ele- CIW ment 3|] is coupled to the electric motor I3. The Y Vlatter is carried by a support 3| which is secured to the casing 23 in such a way that the shaft of the motor I8 is co-axial with the axis of rotation of the drum I'I.

Theunit construction of feeder drum Il, driving motor I8 and reduction gear 28 enables the over-all length thereof to be not greater than the width of the ammunition belt.

Removably secured to the drum-casing 23 is a switch-casing 32 which houses the pair of switches referred to above as indicated at 33 (Figure 3). The leads 35 from the switches 39 pass through the casing 32 to a junction box 33 secured to the outside of said casing, and suitable cables extend from the junction box to the motor I8 and to an electrical battery.

. Eachswitch 34 comprises a switch-block 3l and aspring-lOaded tappet 38 extending therefrom towards an associated cam 39. These cams which are shown at 39a, 3912 in Figure 3 are..

carried by a shaft 4G which extends across the switch casing 32. Secured to the shaft 39 is the floating arm I9 referred to above, the arrangement being such that said arm extends from the Yswitch casing to within the guide casing 33 within which the idler roller 22 is supported by said arm.

Anchored to the floating arm I9 and to the top of the guide casing 33 is a hollow telescopic member 4| which contains the compression spring 29 that is adapted to urge the arm|9 to- Wards the drum Il. The extent to which the oatingarm I9 may be upwardly displaced away from the drum Il is limited by a stop 43 carried by the switch casing.

Above the idler roller 22 there is provided a guide casing 33 with a channel 34 through which the ammunition-belt is fed from said casing to the gun. The channel S acts to deflect the am- ,munition-belt from the vertical path which it `mechanism is required to deal only with the comparatively much shorter length of belt between the drum |'I and the gun.

The operation of the mechanism is as follows: When the gunner presses the gun-firing switch,

the gun commences to operate and draws the belt of ammunition 2| from the auxiliary feed mechanism I6. It is to be noted that the latter is inoperative until the gun has commenced drawing the belt of ammunition from the channel 44. As a consequence the drum I1 will not draw the ammunition belt from the box I5 and feed it into the casing 33 before the length of that part of the belt which lies within the guide casing (that is the portions 2m and 2| b) is reduced. It is this reduction in length of the ammunition-belt by the operation of the guns which is automatically effective in bringing the feed-mechanism I6 into action.

The shortening of the ammunition belt described above displaces the idler-roller 22 in an upward direction and consequently the arm I9 is moved to rock the cam-shaft 4i). The cams Vare designed so that they engage their tappets 3S successively. The switches 34 are thus closed in succession by the displacement of said tappets and in each case a circuit is completed comprising the motor I8 and the battery.

The mechanism has been so designed that shortening of the belt 2| by an amount equivalent to about one-quarter of the diameter of a shell will displace the arm I9 sufficiently for the rst circuit controlled by cam 39a to be completed. When the belt is shortened by an amount equivalent to one-half of the diameter of the shell and a second circuit regulated by cam 39h is brought into operation. It will be seen therefore that even when a single shot is fired, the two circuits will be completed in succession.

The circuit completed by the actuation of the cam 39a includes a resistance in series with the motor I 8 and the battery so that the motor drives the drum I'I at a low speed such that the ammunition belt is fed into the casing 33 more slowly than it is withdrawn through thechannel 4B by vthe gun. The circuit completed by the operation of the cam 39h does not include said resistance and the motor I8 drives the drum Il at a higher rate such that the ammunition-belt is passed into the casing 33 faster than it is being withdrawn by the gun through the channel 44.

In the event that the gunner res a single shot, the feed-mechanism I 6 will be brought into operation by the gun at its lower rate of feed when the belt length within the guide casing is shortened by one-quarter of the shell diameter and at the higher rate of feed when it is shortened by one-half of this diameter. The

Vmechanism will continue to operate to feed the ture of the rst shot and its replacement by the mechanism I6 will take place as described above, the feed-mechanism 4being nally brought into operation at the higher of the two rates of supply. Under these conditions the length of ammunition belt in the guide casing 33 will increase, the floating arm I9 will fall, the circuit for the supply `vatv the higher rate will be cut out by the consequent movement of cam 39h and simultaneously the circuit for supply at the lower rate will be brought into use by cam 39a. The mechanism I6 will then operate at its lower rate of feed, The continued demand of the gun with this low rate of feed effective will result in a shortening of the ammunition belt and as a consequence the low rate of feed circuit is replaced by the high rate of feed circuit. It will be appreciated that under these conditions the mean rate of 'feed by the auxiliary feed mechanism will be equivalent to that at which the belt is being used by the gun.

It is necessary to ensure that when the guns stop firing, either after a single shot or after a short or long burst, the feeder-mechanism i6 continues to operate until the expended shots have been replaced and the ammunition belt lies on the path of J-outline which existed before firing commenced. This requires that the first circuit corresponding to the lower rate of feed by the mechanism remains closed until the iioating arm I9 is completely returned to its undisplaced position although upon shortening of the belt due to firing it is necessary that the arm be displaced by a certain amount (this corresponds to the above mentioned shortening of the belt by one-quarter of the diameter of a shell) before this circuit is completed. To allow for this the oating arm I9 is connected with the cam-shaft 49 through a lostnmoticn device 45. The latter comprises an arm 48 formed integally with the Boating arm I9, a plate 46 carried by the cam-shaft 40, and a pair of fingers 41 carried by the plate 46, the arm 48 being located between said fingers which are spaced apart by an amount slightly greater than the width of the arm. As is clear from Figure 2 the arm 48 will be displaced by an amount corresponding to the distance between its lower edge and the bottom finger 41 before it commences to rotate the cam-shaft 40 and operate its switch 34. On the downward movement of the arm I9, the cam will maintain the switch closed until this lost Inotion has been taken up and the switch is opened by the final movement of the arm I3 to its lowest position.

In order to provide for interchangeability of the parts of the auxiliary feed mechanism when the machine guns are mounted in pairs in the gun turret (as is shown in Figure 1) it is arranged that the motors be capable of driving in a clockwise or anti-clockwise direction since the one installation will be a mirror image of the other.

There may be provided a catch to support that part of the ammunition belt between the feeder drum and the ammunition box so as to prevent its weight from rotating the feeder drum and thereby shortening the circuitous path of that part of the belt between the feeder drum and the gun, Such shortening would close the motor circuits in the manner above described, and when the gun is not in operation, such hunting is undesirable. The catch t may taken any convenient form such that when the feeder mechanism is in operation, the belt overruns the catch, but when the motor is stopped the catch supports the belt. For example, a stop 49 is provided on the drum casing and is pressed into engagement with the sprocket-teeth 21 of the feeder-drum by the spring 50 so that the stop prevents the weight of the ammunition-:belt lying between the ammunition box and the auxiliary feed-mechanism from pulling the belt back through the mechanism.

I claim:

An auxiliary, independent, power driven mechanism for drawing a belt of ammunition towards a machine gun comprising a casing, a member carried within the casing for drivingly engaging the rounds of ammunition of the belt, an electric motor for driving said member, a first switch for starting and stopping said motor, a resistance in series with said rst switch and said motor, a second switch for` cutting out said resistance in the motor circuit, a displaceable arm to engage the belt, means urging the arm to a position at which the belt is constrained to follow a circuitous path and means connecting the displaceable arm with said switches so that the switches are actuated, in succession, to control the motor only by the arm when displaced on shortening and lengthening of the -belt path, the first switch being closed to complete the motor circuit when the belt path is shortened by a small amount so that the motor draws :the belt into the casing at a lower rate than the belt is withdrawn therefrom by the gun and the second switch being closed to complete the motor circuit when the belt path is shortened by a greater amount so that the motor draws the belt into the casing at a higher rate than the belt is withdrawn therefrom by the gun.

EVELYN CECIL MUSCHAMP' DASSIS-FONSECA. y

REFERENCES CITED The following references are of record `in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,285,654 Hanna et al June 9, 1942 2,329,308 Trotter et al Sept. 14, 1943 2,342,065 Trotter et al, Feb. 15, 1944 2,353,639 Berthold et al. July 18, 1944 2,364,309 North Dec, 5, 1944 2,372,750 Tompkins et al. Apr. 3, 1945 2,403,170 Chapman et al July 2, 1946 FOREIGN"PATENTS Number Country Date 690,426 France June 17, 1930 366,247 Italy Dec. 22, 1938 555,267 Great Britain Aug. 13, 1943 

